Spatial Variation in Contaminant Occurrence in Marine Fishes and Prawns from Coastal Tanzania

There are limited data on organic contaminants in marine biota from coastal Tanzania, especially on the occurrence of industrial-use contaminants such as polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). The present study, performed in 2018-2019 in coastal Tanzania and Zanzibar Island, aimed at assessing spatial variation in the occurrence of PCBs; brominated flame retardants (BFRs), including PBDEs; and organochlorine pesticides, including dichlorodiphenyltrichloroethane (DDT), among three locations that differ in degree of anthropogenic activity. Analyzed samples included edible tissues of marine fishes and prawns representing different trophic levels and habitats. The results indicate a mainland-island difference, with fishes and prawns collected on Zanzibar having significantly lower PCB and DDT concentrations but higher concentrations of hexachlorobenzene compared to the two mainland locations. The highest contaminant concentrations were found in fishes and prawns collected around central Dar es Salaam harbor, with median sigma PCBs ranging from 22.3 to 577 ng/g lipid weight and sigma DDTs from 22.7 to 501 ng/g lipid weight, suggesting local sources. Concentrations of PBDEs were similar among locations, suggesting more diffuse sources. None of the newer-type BFRs, including compounds introduced as replacements for PBDEs, were detected in the present study. Stable isotope values of carbon (delta C-13) and nitrogen (delta N-15) varied among locations, and the relationship between contaminants and delta N-15 varied among locations and habitat (pelagic/demersal). Concentrations measured in the present study are below European guidelines for human consumption of fishes and prawns. However, industrial-use contaminants should be monitored in developing countries because they are contaminants of emerging concern as a result of increasing industrialization and global trade of used products and wastes. Environ Toxicol Chem 2022;00:1-13. (c) 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Automated summary

This study aimed to assess the occurrence and spatial variation of industrial-use contaminants in marine biota from coastal Tanzania. The results showed differences in the concentrations of PCBs, BFRs, and organochlorine pesticides among different locations. Samples collected from Zanzibar Island had lower concentrations of PCBs and DDT but higher concentrations of hexachlorobenzene. The highest concentrations of contaminants were found in samples collected around central Dar es Salaam harbor.